Limatulichthys nasarcus, Londoño-Burbano, Alejandro, Lefebvre, Stéphanie L. & Lujan, Nathan K., 2014

Londoño-Burbano, Alejandro, Lefebvre, Stéphanie L. & Lujan, Nathan K., 2014, A new species of Limatulichthys Isbrücker & Nijssen (Loricariidae, Loricariinae) from the western Guiana Shield, Zootaxa 3884 (4), pp. 360-370 : 362-368

Limatulichthys nasarcus , new species

( Fig. 2 , Tables 1 and 2 )

Holotype. MCNG 56560 (ex. AUM 39845), 150.9 mm SL, Venezuela, Orinoco River drainage, Ventuari River, beach below Raudales Tencua, 56 km ESE of San Juan de Manapiare, N 05°02'59'', W 65°40'20'', N.K. Lujan, O. Leon, R. Pajua, 19–20 April 2004.

Paratypes. Seven specimens, all from Venezuela, Amazonas State, Ventuari River drainage: AUM 39845, 1 alc., 122.5 mm SL, 1 cs, 130.7 mm SL, same data as holotype. AUM 39280, 1 alc., 112.2 mm SL, Parucito River at Raudales Salomon, 2.7 km NE of San Juan de Manapiare, N 05°20'46'', W 66°02'00'', N.K. Lujan, D.C. Werneke, O. León, 16 April 2004; ANSP 182816, 1 alc., 129.0 mm SL, Ventuari River, rapids below Salto Tencua, 227 km ESE of Puerto Ayacucho, 114 masl, N 05°03'03'', W 65°37'28'', N.K. Lujan, D.C. Werneke, M.H. Sabaj, T. Carvalho, 0 6 April 2010; MBUCV-V-35730, 1 alc., 137.6 mm SL, same data as AUM 39845. ROM 88302, 1 alc., 122.1 mm SL, same data as ANSP 182816. ANSP 191324, 1 alc., 134.9 mm SL, Ventuari River, downstream end of extensive rocky rapids ca. 1 km below Salto Tencua, 227 km ESE of Puerto Ayacucho, N 05°03'03'', W 65°37'28'', M. Sabaj Pérez, N.K. Lujan, D.C. Werneke, T. Carvalho, S.V. Meza, O. Santaella, 16 April 2010.

Holotype L. nasarcus L. griseus

Percentages in SL 150.9 Min Max Mean Min Max Mean Head length 36.4 21.4 24.2 23.4 17.7 21.0 19.2 Predorsal length 47.9 30.9 33.4 31.7 30.0 34.4 32.0 Posdorsal length 87.3 56.8 62.4 58.1 58.0 63.6 60.6 Posanal length 74.1 48.1 50.9 50.0 49.4 52.8 51.7 Abdominal length 24.1 16.0 18.0 16.8 14.5 18.0 17.0 Thoracic length 20.7 12.9 14.2 14.1 12.5 14.5 13.4 Dorsal fin length 29.8 19.7 21.4 21.2 17.2 22.8 19.8 Pectoral fin length 24.0 15.9 17.5 16.4 14.0 16.8 15.7 Pelvic fin length 21.1 14.0 15.9 14.7 12.0 15.1 13.9 Anal fin length 24.0 15.7 18.0 16.2 13.7 15.6 14.6 Head depth at supraoccipital tip 12.0 6.4 8.0 6.8 5.9 7.8 7.2 Body depth at dorsal fin origin 12.9 7.4 8.8 8.4 7.7 9.1 8.4 Caudal peduncle depth 2.6 1.2 1.9 1.5 1.2 1.7 1.5 Cleithral width 22.8 12.6 16.4 14.7 11.4 13.8 12.2 Distance between origin of pelvic fin and urogenital pore 10.8 6.0 7.4 6.6 6.0 7.1 6.8 Distance between origin of anal fin and urogenital pore 17.0 10.8 12.0 11.3 10.9 12.3 11.5 Body width at dorsal fin origin 21.1 12.8 15.3 14.0 11.9 15.3 12.9 Body width at pectoral fins origin 25.4 16.6 17.6 16.8 13.6 18.3 16.0 Body width at pelvic fins origin 21.8 13.3 15.2 14.3 11.7 15.6 13.0 Body width at anal fin origin 18.9 10.9 13.4 12.5 10.2 13.0 11.6 Body width at caudal fin origin 4.5 2.4 3.0 2.8 2.0 3.2 2.3 Non-types: Seven specimens, all from Venezuela, Bolivar State, Caura River drainage: ANSP 135884, 2 alc., 104.5 and 119.5 mm SL, sandbar along Caura River some 400 m upstream from Cano Barranca-Rio Caura junction, N 07°08'00'', W 65°04'00'', J.E. Bohlke and W.G. Saul, 30 January 1977. ANSP 135900, 1 alc., 80.5 mm SL, sandbar along Caura River at junction of Caño Chuapo and Caura River, N 07°07', W 65°00', J.E. Bohlke and W.G. Saul, 29 January 1977. ANSP 135755, 1 alc., 60.0 mm SL, Urbana (Urbani) River on Maripa-Las Trincheras road, N 07°18', W 65°00', J. E. Bohlke, W.G. Saul, and E. Ferrer-Veliz, 20 January 1977. ANSP 135883, 3 alc., 22.2–92.9 mm SL, sandbar 0.80 km upstream from Jabillal on Caura River, N 06°56', W 64°50', J.E. Bohlke, W.G. Saul, E. Ferrer-Veliz, and local boys, 27 January 1977.

Diagnosis. Limatulichthys nasarcus can be diagnosed from L. griseus by having: anterior abdominal plates half the size of those at center of abdomen (vs. plates similar in size); spots across the entire dorsum, including snout and head, less than half of diameter of naris (vs. indistinct spots larger or equal than diameter of naris); dark well-defined spots on lateral portions of head and opercle, larger than those on dorsum (vs. spots on lateral portions of head and opercle equal in size to those on remainder of body); profile of snout in dorsal view broadly rounded (vs. acutely triangular); head longer (21.4–24.2 SL vs. 17.7–21.0%); and longer anal fin (15.7–18.0 SL vs. 13.7–15.6%).

Description. Head and body strongly depressed. Dorsal profile sloped upward from snout to supraoccipital tip, slightly concave or straight from supraoccipital to caudal peduncle. Ventral profile straight. Snout broad, rounded in dorsal view (see Diagnosis; Fig. 2 ), with rounded anterior margin and convex sides; snout covered with plates. Orbits oriented dorsally, internares space narrower than interorbital space. Orbital notch poorly developed, dorsal margin of orbit not raised.

Upper lip with fringe of usually five triangulate papillae increasing in size laterally, papillae not extending past premaxillary teeth. Row of triangulate papillae extending along margins of lower lip to base of maxillary barbel. Maxillary barbel short, thin, and attached to lower lip via fleshy membrane. Lower lip divided by median furrow with lateral lobes expanded posteriorly to create an emarginated posterior profile. Ventral surface of lower lip having scarce hemispherical papillae. Teeth bilobed, slender. All teeth having medial cuspid larger than lateral. Premaxillary teeth 5–8 per ramus (mode = 7), dentary 6–10 per ramus (mode = 8).

Abdomen covered with contiguous plates from cleithrum to insertion of pelvic fins, plates not organized into distinct patterns. Ventral surface between cleithrum and oral disk having few poorly developed plates in both small and large specimens, with a small region totally lacking plates around the lower lip. Plates missing around pectoralfin insertion. Anterior abdominal plates smaller than central abdominal plates (see Diagnosis; Fig. 3 ) Three preanal plates surrounding urogenital pore. Predorsal region in both juvenile and adult specimens lacking well-developed keels. Two predorsal plates.

Pectoral fin I,6; first branched ray extending posteriorly slightly beyond pelvic-fin origin, first branched ray longer than spine and all other branched rays; posterior margin concave. Pelvic fin I,5; spine shorter or equal in length to branched rays; posterior margin either straight or oblique. Anal fin I,5; origin posterior to vertical through posteriormost dorsal-fin insertion; first three branched rays longer than others; posterior margin convex. Dorsal fin I,7; spine and first branched ray longer than others; spine extended as filament almost twice as long as branched rays; posterior margin obliquely convex. Caudal fin i,10,i; upper caudal ray extended as a filament almost twice as long as branched rays; posterior margin concave.

Color in alcohol. Dorsal base color sandy brown; small, distinct, unorganized black spots distributed across entire dorsum. Three or four conspicuous black spots on lateral margins of the head below the eye, spots larger than those on dorsum ( Fig. 4 ). Five indistinct transversal bands that are similar in color to spots: anteriormost margin of first band at dorsal-fin origin, anteriormost margin of second band at posteriormost tip of dorsal-fin rays when adpressed, anteriormost margin of third band six plates posterior from posteriormost insertion of dorsal fin, anteriormost margin of fourth band four plates posterior to the third band, and anteriormost margin of fifth band two plates anterior to caudal-fin origin. All fins except anal fin with black dots. Pectoral fins with spots both on membrane and rays, while on other fins spots only present on rays. Anal fin hyaline. Caudal fin with a noticeable horizontal black band across posterior half of the lower branched rays ( Fig. 2 ). Ventrum uniformly pale yellow. Sexual dimorphism: None observed.

Distribution. Known from the middle Ventuari and lower Caura rivers, Orinoco River drainage, Venezuela ( Fig. 5 ).

Etymology. The specific epithet nasarcus is a combination of the Latin nasus meaning snout, and arcus meaning bow-shaped, in reference to the rounded snout of the species when compared to its congener Limatulichthys griseus .

Remarks. As part of our comparative analysis, we examined two Limatulichthys cf. griseus specimens from the Beni River, Amazon Basin, Bolivia (AUM 28353) that were morphologically similar to L. nasarcus . According to the PCA analysis ( Fig. 6 ), though, Limatulichthys cf. griseus ‘Beni’ can still be separated from L. nasarcus by presenting a narrower head and longer snout—characters that are shared with L. griseus . We therefore tentatively identify these specimens as L. cf. griseus ‘Beni’ due to the limited number of specimens available and the tremendous geographic distance between the populations analyzed here.

Figures

FIGURE 2. Holotype of Limatulichthys nasarcus n. sp., MCNG 56560, 150.9 mm SL, Venezuela, Orinoco River drainage, Ventuari River, beach below Raudales Tencua, 56 km ESE of San Juan de Manapiare, latitude 05 ° 2 ’ 59 ’’ N, 065 ° 40 ’ 20 ’’ W, N. K. Lujan, O. Leon and R. Pajua, 19 – 20 April 2004 (photo by NKL).

FIGURE 3. Abdominal plates pattern in (A) Limatulichthys griseus and (B) Limatulichthys nasarcus n. sp. AAP = Anterior abdominal plates; CAP = Central abdominal plates.

FIGURE 4. Lateral view of head of Limatulichthys nasarcus n. sp. (holotype) showing characteristically dark and large spots along the lateral margin (photo by NKL).

FIGURE 5. Map of southern Venezuela and western Guiana shield showing type locality (white star) and distribution of Limatulichthys nasarcus n. sp. (orange squares represent type specimens, whereas non-type specimens are represented by green squares); Limatulichthys griseus (blue circles); and Lim. cf. griseus (purple circles).

FIGURE 6. Size-corrected PCA for components 1 and 2, showing differentiation between morphological characters of the head region. On PC 1: head width (HW), snout width at anterior margin of nares (SW), and width of head at upper lip (LW) loaded most positively. PC 2: Opercular length (OL), snout length (SL), and distance from tip of snout to nasal loaded most positively (SN), while interorbital distance (ID) loaded most negatively. Symbols as in Figure 5; Limatulichthys cf. griseus “ Beni ” (red circles).

Tables

TABLE 2. Comparative meristics for Limatulichthys nasarcus n. sp. and L. griseus.

		L. nasarcus		L. griseus
Counts	Holotype	Min Max	Mode	Min Max	Mode
Lateral plates of median series	17	17 18	18	17 18	18
Lateral plates of mid-ventral series	20	19 20	20	19 20	20
Coalescent plates	11	10 11	11	10 11	11
Ventrolateral thoracic plates	5	5 6	6	5 6	6
Premaxillary teeth	8	5 8	7	6 13	9
Dentary teeth	10	6 10	8	7 14	11
Dorsal fin rays	i-7	i-7 i-7		i-7 i-7
Pectoral fin rays	i-6	i-6 i-6		i-6 i-6
Pelvic fin rays	i-5	i-6 i-5		i-6 i-5
Anal fin rays	i-5	i-5 i-5		i-5 i-5
Caudal fin rays	i-10-i	i-10-i i-10-i		i-10-i i-10-i